Lubricant



ct. 3, i950 LUBRICANT Theodore W. Evans, Oakland, and Richard Whetstone, Berkeley, Cali1'., assignors to Shell Development Company, San Francisco, Cali1'., a corp'oration oi Delaware No Drawing. Application October 8, 19 16,

7 Serial N 0. 792,058

16 Claims.

This invention is directed to novel lubricating compositions, and more particularly it is concerned with novel polymeric lubricants derived at least in part from unsaturated esters.

Mineral oil fractions have been used for many lubricating purposes, but it is well-known that such lubricants possess certain inherit limitations, such as tendency to oxidize, to thicken at low temperatures, etc. A large number of additives have been employed with mineral oils in order to improve these shortcomings. To a certain degree the resulting compositions may be used successfully for most lubricating purposes, but lacquer formation increases as the amount of additives in the oil is raised.

Various synthetic lubricants have been proposed from time to time. These include polymers of cracked wax oleflns, alkylated aromatics such as alkylated naphthylenes, and so on. Some of these are useful for special purposes, but, especially if the previously known synthetic lubricants were derived from olefinic sources, they usually possess corrosion and oxidation characteristics limiting their utility to a substantial degree. Another type of synthetic lubricant which has been previously investigated is alkylene oxide polymer type, such as polymerized propylene oxide.

Polymers are known which have been prepared from the esters of unsaturated aliphatic alcohols, and saturated aliphatic mono-carboxylic acids. However, the polymers are either of a resinous or viscous consistency and have been suggested for only a few specialized purposes, such as plasticizers for. synthetic molding compositions, etc. A

It is an object of this invention to provide new non-hydrocarbon lubricants. It is another object of this invention to provide new lubricating compositions having improved corrosion characteristics. It is still another object of this invention to provide a new method of lubrication. Other objects will become evident from the following discussion.

Now, in accordance with this invention, it has been discovered that polymeric esters of saturated aliphatic monocarboxylic acids and unsaturated aliphatic alcohols may be used as bases for lubrieating compositions. Further in accordance with this invention it has been found that such lubricating compositions may be improved by the additinn of certain corrosion inhibitors, such as alkyl may be improved still further by the combination therein of an oxidation inhibitor such as an aromatic amine with a corrosion inhibitor such asan alkyl phosphite.

Saturated aliphatic monocarboxylic acids which may be esterifled and subsequently polymerlzed to form the subject lubricants have the eneral formula those in which the R1 in the above formula has from about 5 to about 12 carbon atoms.

This group R1 may contain non-hydrocarbon substltuents such as oxygen, sulfur, phosphorus,

wherein R2 is an unsaturated aliphatic radical, and preferably is an oleflnic hydrocarbon radical having from 2 to 20 carbon atoms. These alcohols include allyl type alcohols, methallyl type alcohols, and cinnamyl type alcohols. The-preferred group of these alcohols are the allyl type alcohols, including alpha-allyl alcohol, beta allyl alcohol,

gamma-allyl alcohol, 2-butene-1-ol, 3-butene-3- o1, 3-pentene-2-ol, etc.- Other suitable alcohols include 1-pentene-3-ol, 3-pentene-2-ol, 4-pentene-l-ol, 5-hexene-3-ol, S-octene-l-ol, and their homologs and analogs. Again, as in the case of the above acids, the group R2 of the above formula WA was may contain various non-hydrocarbon substituents, but the most preferred polymeric lubricants are prepared from esters wherein R2 is an olefinic hydrocarbon radical.

The esters of the above alcohols and acids may be prepared, for example, by heating at least one of the acids with at least one of the alcohols in the presence of an esterification catalyst such as para-toluenesulfonic acid; however, mixtures of these acids and alcohols may also be used. The reaction is usually conducted in an azeotropically distilling solvent such as benzene or toluene, so that water of esterification may be conveniently removed. Under these conditions from about to about 20 hours are usually required for complete esterification, although more extended periods may be required if one or more of the reactants is sterically hindered, as in the case of Z-ethylhexoic acid. The ester may be subsequently purified by removal of solvent, catalyst and unconverted constituents. If a mixture of acids or alcohols, such as those obtained from natural sources is used, it may be desirable to fractionate the. products by distillation, adsorption or selective solvent extractionin order to obtain the fraction from which the best polymeric lubricants may be prepared.

The polymeric lubricants may be prepared from the above esters by heating the latter in the presence of certain catalysts. The preferred catalysts are organic peroxides, such as diacyl peroxides, ketone peroxides, aldehyde peroxides, dialkyl peroxides and hydroperoxides. The polymerization preferably is carried out at temperatures from about 100C. to about 250 C., dependent in part upon the activity and stability of the catalyst being employed.

As usual in polymerization reactions, the product is a mixture of polymers of varyin molecular weight, in addition to limited quantities of unpolymerized materials or other low molecular weight substances. "While the mixture so obtained may be useful for many purposes, it is ordinarily useless as a lubricant, due to the presence of more or less volatile fractions. Therefore, it is an essential feature in the preparation of the present lubricating compositions that the more volatile fractions be removed from the polymeric product, preferably by fractional distillation under subatmospheric pressure. Preferably, all fractions distilling below about 100 C. at 2 mm. mercury pressure are removed, thus leaving a fraction having lubricating characteristics.

If the polymerization is carried to the point where the product contains an unduly large resinous or solid fraction it may be preferable to remove not only the relatively volatile fraction but also at least a part of the solid fraction, thus isolatin the portion having intermediate molecular weights for lubricating purposes. However, the higher molecular weight products may be combined with more fluid lubricants such as polymeric hydrocarbons, alkylene oxides, alkylene glycols, etc. to impart a higher viscosity thereto and to otherwise alter lubricatin properties. Likewise, modified synthetic lubricants are obtained by combining polymeric hydrocarbons, alkylene oxides, or alkylene glycols with the liquid polymeric lubricants described herein. In order to obtain maximum stability, it is desirable at times to hydrogenate the polymeric lubricants described herein in order to reduce any residual unsaturation.

Typical polymers from which lubricating fracnate, allyl caprate, allyl methoxy-acetate, allyl beta-ethoxypropionate, allyl phenoxyacetate, as well as their polymerizable analogs and homologs.

The subject lubricants may be prepared to form a wide variety of compositions having low pour points, high viscosity indices, and other desirable lubricating properties. Pour points of 20 F. to F. are readily obtained, and viscosity indices vary from '75 to 145. Lubricants of any SAE number from less than 10 to more than 80 may be prepared.

These polymeric lubricants are reasonably stable to oxidizing influences, and show an excellent response to oxidation inhibitors, especially aromatic amines such as mononuclear aromatic amines, including 2-hydroxy-5-nitroaniline, paraanisidine, and 2,4-xylidene; monocyclic aromatic diamines such as N,N-dibutyl-para'phenylenediamine, 2,4-diamino-toluene, and para-phenylenediamine; aminophenols such as paraphenylaminophenol, di(para-hydroxyphenyl) amine, and para-butylaminophenol; polynuclear aromatic diamines such as N,N-diphenyl-paraphenylenediamine, N (4 hydroxyphenyl) -N'- phenyl para phenylenediamine, and N,N'-di- (para-hydroxyphenyl) para-phenylenediamine; as well as polycyclic aromatic amines such as phenyl-alpha-naphthylamine.

Preferably, the aromatic amine is present in amounts varying from about 0.1% to about 5%, by weight, but it is preferred practice to us the minimum amount necessary to obtain the stability required.

It has been found that corrosion of bearings and other metal parts due to use of the subject lubricants is reduced by modifying the latter with an anti-corrosion agent, especially the organic phosphites such as the alkyl phosphites, the aryl phosphites and mixed alkyl-arylphosphites.

The phosphites which impart maximum anticorrosion properties to the compositions of the present invention are the trialkyl phosphites, each alkyl group thereof having from about 1 to about 12 carbon atoms. These include trimethyl phosphite, triethyl phosphite, tripropyl phosphite, triisopropyl phosphite, tributyl phosphite, triamyl phosphite, trihexyl phosphite, triheptyl phosphite, trioctyl phosphite, trinonyl phosphite, tridecyl phosphite, tridodecyl phosphite; and mixed alkyl phosphites such as methyl dibutyl phosphite, dimethyl butyl phosphite, etc.

The alkylphosphites are particularly-= effective in the compositions of the present invention if they are present in amounts from about 0.2% to about 6%, preferably from about 0.5% to about 2.5%. The best lubricating results are obtained if an aromatic amine is combined with one of the above types of organic phosphites in the compositions of the present invention. By following this procedure a composition having minimum corrosion characteristics is obtained, since some of the decomposition products formed in the absence of aromatic amines are somewhat corrosive, especially to copper-lead bearings.

Other constituents may be present in the subject lubricating compositions, such as extreme pressure additives. The adducts of olefins and hydrogen sulfide or mercaptans are suitable for this purpose, especially if they have been reacted with sulfur to give sulfur contents from about to about 60%. An especially effective extreme pressure agent is the peroxide catalyzed adduct of diallyl ether and hydrogen sulfide which has been reacted with sulfur, the final product containing from about to about 45% combined sulfur, Since these adducts have lubricating properties as well as extreme pressure properties, they may be present in any concentration, especially from about 2% to 50% by weight of the total composition.

The subject lubricants may be employed in the form of greases, by using metallic soaps such as wherein n is an integer and R is a saturated aliphatic hydrocarbon radical. Suitable polymers include those of propylene oxide, trimethylene glycol, hexamethylene glycol, etc. From about 3% to about 20% by weight of the subject protective colloids in the present grease compositions will insure the homogeneity thereof.

The subject lubricating compositions are useful as engine lubricants, greases, cutting oils, textile machinery oils, stand-by protective coatings, etc. Their use results in low lacquer, piston crown, piston ring and sump deposit formation, and the wear characteristic of the lubricants are satisfactory. V

The following examples illustrate the lubricating characteristics of the compositions of the present invention.

EXAMPLE I A polymer of allyl caprylate was heated in a carbon dioxide atmosphere for 24 hours at 150 C. in order to determine its thermal stability. Data obtained before and after the heat treatment are given in the table below:

Before iivrn Alter l-lent Treatment lrvuinunt Viscosity, ccntistokes at 100 F 83. 5 80. 6 Viscosity, centismkcs at 210 F 11,85 i2. 13 Viscosity index 130 129 RAE Grade 8O EXAMPLE II heating at the various temperatures are given in the table below:

Jar ris I19 85 I10, T mm m. Weight Weight Per Cent Per Cent 89. 5 2.0 13 1. o 46 as 19. a a. 4

Use of additives in poly (allyl caprylate) A polymer of allyl caprylate was modified with 1% by weight of tributyl phosphite and 1% of phenyl-alpha-naphthylamine, The resulting lubricant had the following properties:

Viscosity, centistokes at F. 74.4 Viscosity, centistokes at 210 F 11.72 Pour point, F -45 Viscosity index 137 SAE grade 30 The lubricant was subjected to the thermal stabillty test described in Example I. There was an increase of 4.5% in viscosity (210 F.) and a loss of 2 in viscosity index caused by the heat treatment.

The lubricant also was subjected to the oxidation test described in Example IV. It required 30 hours for the oxygen pressure to drop 10 p. s. i. and 71.5 hours for the pressure to drop 20 p. s;' i. The rate of oxidation was constant throughout the entire period of testing.

A standard Lauson engine test was performed on the lubricant, running the engine for 40 hours at a Jacket temperature of 100 F. There was low bearing corrosion, moderate lacquer formation, moderate change in viscosity of the lubricant, moderate oil consumption and normal piston and sump deposits.

EXAMPLE IV A polymer of allyl caprylate was inhibited with 1 wt. of phenyl-alpha-naphthylamine. Seventy-five grams of the lubricant were oxidized at C. under an initial oxygen pressure of 50 p. s. i. in the presence of '75 sq.- cm. of copper. It required 42 hours for the oxygen pressure to drop 10 p. s. i., and 81 hours for it to drop 20 p. s. i. The rate of oxidation was steady throughout the entire period (1. e. the induction period was greater than 81 hours). When 1.5% phenyl-alpha-naphthylamine was present, it required 67 hours for the pressure to drop 10 p. s. i. and 138 hours for a, drop of 20 p. s. i. The rate of oxidation was constant throughout the entire period of testing.

.. EXAMPLE v Poly (allyl caprylate) was usedas an engine lubricant in a standard Lauson engine. the test being conducted for 40 hours at a jacket temperature of 100 F. The lacquer rating and oil consumption were low, there was moderate hearing corrosion, the deposits on piston crown and rings were light, and there was no'sludge in the soil cump. The lubricant contained 0.5% phenylalpha-naphthylamine.

We claim as our invention:

1. A lubricating grease comprising, as substantially the sole lubricant present, a major amount of a liquid polymerized ester of a saturated monocarboxylic acid having between 5 and 12 carbon atoms and an unsaturated aliphatic monohydric alcohol having between 3 and 8 carbon atoms, said polymerized ester having a minimum boiling point above 100 C. at 2 mm. mercury pressure, and a'minor amount of an alkali metal soap sufficient to form a uniform grease structure.

2. A lubricating grease comprising, as substantially the sole lubricant present, a major amount of a liquid polymerized ester of a saturated monocarboxylic acid having between and 12 carbon atoms and an unsaturated aliphatic monohydric alcohol having between 3 and 8 carbon atoms, said polymerized ester having a minimum boiling pointabove 100 C. at 2 mm. mercury pressure, a minor amount of an alkali metal soap sumcient to form a uniform grease structure and a minor amount, suflicient to inhibit corrosion, of a trialkyl phosphite.

3. A lubricating grease comprising, as substantially the sole lubricant present, a. major amount of a liquid polymerized ester of a saturated monocarboxylic acid having between 5 and 12 carbon atoms and an unsaturated aliphatic monohydric alcohol having between 3 and 8 carbon atoms, said polymerized ester having a minimum boiling point above 100 C. at 2 mm. mercury .pressure, a minor amount of an alkali metal soap sumcient to form a uniform grease structure, and a minor amount, sumcient to inhibit oxidation, of an aromatic amine.

4. A lubricating grease comprising a major amount of a liquid polymer ofallyl caprylate, said polymer having a minimum boiling point of 100 C. at 2 mm. mercury pressure, and a minor amount of an alkali metal soap, sufiicient'to form a uniform grease structure.

5. A lubricating grease comprising a major amount of a liquid polymer-of allyl caprylate,

said polymer having a minimum boiling point of 100 C. at 2 mm. mercury pressure, and a minor amount of soda soap. sufficient to form a uniform grease structure.

6. A lubricating grease comprising a major amount of a liquid polymer of allyl caprylate, said polymer having a minimum boiling point of 100 C. at 2 mm. mercury pressure, and a minor amount of lithium soap, sufiicient to form a uniform grease structure.

"I. A lubricating grease comprising a major amount of a liquid polymer of allyl caprylate, said polymer having a minimum boiling point of 100 C. at 2 mm. mercury pressure, and a minor amount of soda soap, suflicient to form a uniform grease structure and a minor amount, sufficient to inhibit corrosion of trioctyl phosphite.

8. A lubricating grease comprising a major amount of a liquid polymer of allyl caprylate, said polymer having a minimum boiling point of 100 C. at 2 mm. mercury pressure, and a minor amount of lithium soap, sufficient to form a uniform grease structure and a minor amount, sufficient to inhibit corrosion of trioctyl phosphite.

9. A lubricating grease comprising a major amount of a liquid polymer of allyl caprylate, said polymer having a minimum boiling point of 100 C. at 2 mm. mercury pressure, and a minor amount of soda soap, sufficient to form a uniform grease structure and a minor amount, sufficient to inhibit oxidation of phenyl alphanaphthylamine.

10. A lubricating grease comprising a major 100 C. at 2 mm. mercury pressure, and a minor amount of lithium soap, sufficient to form a uniform grease structure and a minor amount, sufficient to inhibit oxidation of phenyl alphanaphthylamine.

11. A lubricating grease comprising a major amount of a liquid polymer of allyl caprylate, said polymer having a minimum boiling point of 100 C. at 2 mm. mercury pressure, a minor amount of alkali metal soap, sufiicient to form a uniform grease structure and a minor amount, sufiicient to inhibit corrosion, of trioctyl phosphite.

12. A lubricating greas comprising a major amount of a. liquid polymer of allyl caprylate, said polymer having a minimum boiling point of 100 C. at 2 mm. mercury pressure, a minor amount of alkali metal soap, sufiicient to form amount of a liquid polymerof allyl caprylate,

said polymer having a minimum boiling point of a uniform grease structure and a minor amount, suflicient to inhibit oxidation, of phenyl-alphanaphthylamine.

13. A lubricating grease comprising a major amount of a liquid polymer of allyl caprylate, said polymer having a minimum boiling point of C. at 2 mm. mercury pressure, a minor amount of alkali metal soap, sufficient to form a uniform grease structure and a minor amount, sufiicient to inhibit oxidation, of an aromatic amine.

14. A lubricating grease comprising a major amount of a liquid polymer of allyl caprylate, said polymer having a minimum boiling point of 100 C. at 2 mm. mercury pressure, aminor amount of alkali metal soap, sufilcient to form a uniform grease structure and a minor amount,

sumcient to inhibit oxidation of an N-aryl naphthylamine.

15. A lubricating grease comprising a major amount of a liquid polymer of allyl caprylate, said. polymer having a minimum boiling point of 100 C. at 2 mm. mercury pressure, a minor amount of alkali metal soap, sufiicient to form a uniform grease structure and a minor amount, sufiicient to inhibit corrosion, of a trialkyl phosphite.

16. A lubricating grease comprising a major amount of a liquid polymer of allyl caprylate, said polymer having a minimum boiling point of 100 C. at 2 mm. mercury pressure, a minor amount of an alkali metal soap, sufficient to form a uniform grease structure, a minor amount, suificient to inhibit corrosion, of a trialkyl phosphite and a minor amount, sufficient to inhibit I oxidation, of an aromatic amine.

THEODORE W. EVANS. RICHARD WHETSTONE.

REFERENCES CPEED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

1. A LUBRICATING GREASE COMPRISING, AS SUBSTANTIALLY THE SOLE LUBRICANT PRESENT, A MAJOR AMOUNT OF A LIQUID POLYMERIZED ESTER OF A SATURATED MONOCARBOXYLIC ACID HAVING BETWEEN 5 AND 12 CARBON ATOMS AND AN UNSATURATED ALIPHATIC MONOHYDRIC ALCOHOL HAVING BETWEEN 3 AND 8 CARBON ATOMS, SAID POLYMERIZED ESTER HAVING A MINIMUM BOILING POINT ABOVE 100*C. AT 2 MM. MERCURY PRESSURE, AND A MINOR AMOUNT OF AN ALKALI METAL SOAP SUFFICIENT TO FORM A UNIFORM GREASE STRUCTURE. 